Attached is a test-case boiled out of OpenOffice.org and bolted onto the xlib
cairo-demo. It attempt to render the string MoWoW and the string MWooW with a
very large Liberation Serif font. And the screenshot shows the results. Unless
I'm being very slow today (always possible) there is something terribly screwed
up going on.
cairo-1.6.4-1.fc9.i386
I see this both with a i810 driver and a nv driver.

I've replicated this bug with the r100 driver as well. So it appears to be
a fairly generic cairo-xlib or X server bug. Note that the bug does not appear
when rendering to a cairo image surface. Also, the bug is present with at least
both of "Liberation Sans" and "Bitstream Vera Sans".
-Carl

(In reply to comment #5)
> Isn't this the bug reported here:
> http://lists.cairographics.org/archives/cairo/2008-May/014033.html
Could be. I hadn't done any analysis of that one, so hadn't remembered it.
No fix yet?
Behdad, does Vlad's suggestion sound right?
I'm still looking close to try to understand this one myself. Where is
the glyph data getting shuffled for example?
-Carl